The present application relates to multi-unit railroad freight cars, and in particular to the attachment of inter-unit articulated connectors to center sills of car units.
Multi-unit railroad freight cars, such as well cars for transporting stacked intermodal containers, utilize articulated connectors in the form of male and female castings that mate with one another to interconnect adjacent car units. The articulated connectors are connected to the car units by being welded to center sills that in some car units are tubular stub center sills welded to the undersides of body bolsters.
Not only do the articulated connectors carry the weight of a car unit and its lading to the top of a shared wheeled truck between a pair of adjacent car units, but they also have to carry lateral forces resulting from when the car negotiates a curve in a track and the draft and buff forces between cars and car units cumulatively resulting from moving the car along with others in a train.
After lengthy use, for example 1.5 million miles, the articulated connectors of a multi-unit railroad freight car need to be replaced. In the past this has been difficult, because some of the welds attaching an articulated connector to a center sill of a car unit are located within the center sill. This was thought necessary in the past in order to have enough welded metal to transmit the draft and buff train forces resulting from operating such multi-unit cars in trains that may weigh as much as 40 million pounds. Those forces must be carried from each articulating connector into each car unit through the center sill to which the connector is attached.
Each articulated connector unit includes a respective male or female coupling portion designed to extend from a center sill toward the shared truck and the adjacent car unit. An outer portion of each articulated connector unit abuts against the extreme end of the center sill to which it is attached, and another portion of the articulated connector extends for a distance inside a box beam structure of the center sill.
While welds at the extreme end of a center sill have always been used to attach an articulated connector, it was previously also considered necessary to have additional welds. In the past, additional welding has attached the portion of the articulated connector extending inside the center sill to the interior of the center sill. This was thought necessary to ensure that the connection of the articulated connector to the center sill is capable of carrying the magnitude of forces that may be experienced when such a multi-unit freight car is operated as part of a long, fully-loaded train.
Consideration was given to the use of slot welds, but slot welds have not proven practical, and so welds inside the box structure of a center sill have been used instead.
Because of the welds located within the center sill it has been necessary to cut into the center sill to detach a worn articulated connector so that a new articulated connector can be installed. When another connector is installed similar welds have had to be used and openings made in the center sill have had to be closed. These procedures have required an undesirable amount of labor. It is therefore desired to attach an articulating connector to a stub center sill in a manner that provides sufficient strength without the requirement for internal welds within a center sill.